With the continuously shrinking of the size of semiconductor devices, the conventional gate dielectric material made of silicon oxide becomes thinner and thinner, thus problems such as power consumption wasting and heat generation have emerged. These problems may have been solved by the hafnium-based high-K dielectric material and metal gate process. For example, the switching power consumption and the leakage current from source to drain of transistors formed by the new type of 45 nm process which uses the hafnium-based high-K dielectric material and metal gate process are reduced, the leakage current of the gate oxide layer is also reduced, and the switching speed of the transistors is significantly increased.
However, the performance of PMOS transistors formed by the existing fabrication processes including the above mentioned hafnium-based high-K dielectric and metal gate process may still need improvements. Therefore, new techniques for fabricating PMOS transistors are needed to improve the performance characteristics of PMOS transistors. The disclosed methods and systems are directed to solve one or more problems set forth above and other problems.